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Method to produce aggregates from unsettled cementitious mixtures

a cementitious mixture and aggregate technology, applied in the field of method to produce aggregates from unsettled cementitious mixtures, can solve the problems of not being foolproof with said method, not revealing a method to predict, and concrete returned represents a loss to concrete manufacturers

Inactive Publication Date: 2018-06-14
CEMEX INNOVATION HLDG LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention relates to a method using a pelletizing agent and superplasticizers in hydraulic cement compositions to improve their workability and rheological properties. The pelletizing agent is made of acrylamide-based, which is effective and easily available in the market at a low cost. Superplasticizers prevent particle aggregation and reduce water demand while maintaining a good dispersion of cement particles, resulting in improved hydration reaction. Overall, this technology helps create better quality cement and concrete.

Problems solved by technology

Another example of concrete that may not be used and therefore is returned to the plant is when, due to a poor mix design, during the handling, transporting and placing, the cement paste and fine aggregates are separated from the coarse aggregates.
In any case, returned concrete represents a loss to the concrete manufacturer, since it is product that has been fabricated and cannot be sold.
Nevertheless, said method is not foolproof and new solutions are being studied to deal with the issue.
Also, JP 3147832 U does not disclose a method to predict the properties of the granular material obtained, namely the particle size, Los Angeles of the particles produced or the time to produce the pellets, like the present method does.
In addition, EP 2468695 shows no direction on how to predict the properties of the granular material obtained.
In conclusion, the prior art has not so far disclosed a method to produce aggregates with predictable size and tailored to diverse applications in the construction industry sector.
The problem to be solved is providing a method to reuse returned cementitious mixtures that would normally be disposed of, to produce materials that can be used as coarse aggregates in fresh concrete mixtures.

Method used

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  • Method to produce aggregates from unsettled cementitious mixtures
  • Method to produce aggregates from unsettled cementitious mixtures
  • Method to produce aggregates from unsettled cementitious mixtures

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0089]To test the characteristics of concrete where part of its aggregates is substituted by the pelletized material, lab tests were performed. First, a returned concrete was simulated having the following mix design:

TABLE 3Mix Design of the returned concreteMATERIALUNITMIX 1CEM I 52.5 Rkg / m3330Fly ashkg / m30Limestone fillerkg / m30w / b total—0.71w / b eff—0.6Sand 0 / 4 roundkg / m3807Gravel 4 / 8 crushedkg / m3359Gravel 8 / 11 crushedkg / m3609Superplasticizer% mass of cem  1%Retarder% mass of cem0.20%Pelletizing agentkg / m32.1

[0090]Slump flow at 5 minutes was 680 mm (SF2).

[0091]All the components, except the pelletizing agent, were mixed for a couple of minutes. The pelletizing agent was then added. The mixes were then stirred for 5 minutes, after which the materials were completely pelletized.

[0092]Pellets were discharged into a pile and left to dry at a temperature of 17° C. for 29 hours.

[0093]Table 4 summarizes the characteristics of the pellets obtained:

TABLE 4Properties of the recycled aggregat...

example 2

[0095]A concrete with the mix design described in Table 5 was sent to a job site but was partially returned to the plant.

TABLE 5Mix design of the returned concreteConcrete mix designCEM I 52.5 N[kg / m3]350   w / c[—]0.570 / 4 round[% agg volume]42%4 / 8 round[% agg volume]26%8 / 12 round[% agg volume]32%Plasticizer[% mass cement]1.70% Retarder[% mass cement]0.35% Slump[cm]17.5 Workability class[—]S4

[0096]At the plant, 1.35 kg / m3 of pelletizing agent was added to the concrete inside the truck and mixed during 6 minutes, at a rotation speed of 14 rpm.

[0097]After these 6 minutes, the material was completely agglomerated into pellets. They were discharged from the mixer forming a pile and were left to curing. Since the external temperature was 22° C., the pile was left to dry during 24 hours.

[0098]The recycled aggregates produced had the following characteristics:

TABLE 6Recycled aggregates characteristicsD10 = 2.8 mmD50 = 8.3 mmD90 = 15.8 mmD90 / D10 = 5.64L.A. = 38

[0099]According to Table 6, mono...

example 3

[0100]A concrete mix design with the following characteristics was produced:

TABLE 7Mix designConcrete mix designCEM III 42.5 R[kg / m3]325   Fly ash[kg / m3]75   w / binder[—]0.470 / 2 round[% agg volume]32%2 / 10 crusehd[% agg volume]41%10 / 16 crushed[% agg volume]27%Superplasticizer[% mass binder]2.14% Defoaming agent[% mass binder]0.05% 

[0101]Table 8 summarizes the fresh properties of this concrete:

TABLE 8Fresh PropertiesFresh propertiesSlump flow[cm]71.5Workability class[—]SF2

[0102]Part of this concrete was returned to the plant. 2.9 kg / m3 of pelletizing agent was added to the concrete truck's mixing drum and mixing was done for 4.5 minutes at a rotation speed of 16 rpm. The pellets were discharged into a pile and left to dry at a temperature of 25° C. for 16 hours.

[0103]The Particle Size Distribution of these pellets was done and summarized in table 8:

TABLE 9Particle Size Distribution of the produced pelletsParticle Size DistributionSievePassing[mm][%]63100.00%31.6100.00%2091.57%1687.63%1...

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Abstract

Method to produce aggregates from unsettled cementitious mixtures, comprising the steps of (a) adding at least one pelletizing agent to an unsettled cementitious mixture, (b) mixing constantly the mixture of step (a) in a mixer to produce pellets, (c) discharging the pellets obtained in step (b) and (d) drying the pellets formed in step (c). The pelletizing agent is selected from the group consisting of cellulose, chitosan, collagen, polyacrylamide and co-polymers of polyacrylamide and polyacrylics, polyamines, polyvinylalcohols, polysaccharides, lactic acid, methacrylic acid, methacrylate, hydroxyethyl, ethylene glycol, ethylene oxide, acrylic acid, inorganic flocculants and inorganic coagulants.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a method to produce aggregates from unsettled cementitious mixtures. Particularly, the present invention relates to a method to prepare pellets with predicted particle size from fluid cementitious materials, to be used in diverse applications, including but not limited to substitution of aggregates in concrete mixtures for various functions. Furthermore, through this method one can produce aggregates with predicted particle size from any kind of unsettled cementitious mixtures, for example from mixtures with high fluidity, high binder content, low gravel to sand ratio and / or with high admixtures content.BACKGROUND OF THE INVENTION[0002]On a daily basis, a significant amount of concrete produced at a ready-mix plant is not used. For example, contractors normally order an extra amount of concrete than the one needed for the job in hands, in order to account for unexpected setbacks, for example, shortage of concrete due to er...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C04B18/02C04B24/02C04B24/12C04B24/26C04B24/38
CPCC04B18/021C04B24/02C04B24/121C04B24/2623C04B24/2641C04B24/2652C04B24/383C04B24/38
Inventor ZAMPINI, DAVIDEGUERINI, ALEXANDREVOLPATTI, GIOVANNI
Owner CEMEX INNOVATION HLDG LTD
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